During the 15-minute call, Obama spoke of a "unique opportunity" to make progress with Iran's new leadership, amid a flurry of diplomacy over its nuclear programme. It was the first communication between US and Iranian leaders since 1979.

Describing his conversation as a starting point, Obama said he believes an agreement was possible regarding Iran's nuclear ambitions that could lead to better relations, a website reported.

"While there will surely be important obstacles to moving forward and success is by no means guaranteed, I believe we can reach a comprehensive solution," said Obama during a White House briefing.

Meanwhile, Obama raised concerns about American prisoners in Iran, but the bulk of the call was about efforts to reach a solution on the nuclear issue.

Earlier, Rouhani, who was elected as Iranian president in June and viewed as a moderate leader, expressed his country's keenness to reach a deal soon. He also asserted that Iran did not seek a nuclear bomb, contrary to what western powers have long suspected.

Describing meetings at the UN this week as a "first step", Rouhani said he believed the nuclear issue could be settled "within the not too distant future", a website reported.

The Iranian president said initial discussions had taken place in an environment that was "quite different" from the past.

The call with Obama was made just before Rouhani left New York, where he has been attending the annual summit of the UN General Assembly, according to Iranian news agency IRNA.

White House officials described the conversation - apparently initiated by Rouhani - as cordial.